1. Field of the Invention
The present invention relates to a power supply device that can easily and rapidly constitute an uninterruptible redundant power supply device capable of driving a load by means of a rectified output from a commercial alternating current (AC) power supply during normal operation and driving the load by means of an output from a secondary cell or other DC power supply during abnormal operation such as during a power outage, for example. More particularly, the present invention relates to a power supply device that can be converted into an uninterruptible redundant power supply device that is used in order to operate highly important devices such as precision instruments and automated machineries which are directed toward crime prevention, disaster prevention, communications, information (server computers, FA personal computers, and so forth), and medical care. Here, a power outage indicates that the electrical power (current) supply is disconnected, and indicates cases where the supply of power from an electric power company is cut, and cases where the power supply is cut due to the failure of a breaker, a plug being disconnected, or a wire break, and so forth, for example.
2. Description of the Related Art
Although there is a need for uninterruptible redundant power supply devices because of the requirement for continuous uninterrupted operation over a 5-year duration 24 hours a day, or similar, when the above-mentioned power supply device is used for a server computer or similar, for example, the need for uninterruptible redundant power supply devices is low due to the problem of the steep rise in costs of computers used by individuals (personal computers). However, the present state of affairs is that, in addition to users requiring low-cost power supply devices that can be used only when commercial AC power supplies are working normally, that is, ordinarily, uninterruptible redundant power supply devices that permit devices to be employed even during abnormal operation such as during a power outage are required, and therefore two types of power supply devices are manufactured.
Furthermore, there is sometimes a need for a power supply device that differs from an uninterruptible redundant power supply device capable of dealing with a power outage, that is, a power supply device embedded with an output terminal for outputting a desired voltage, and hence, in addition to the two above-mentioned types of power supply device, a total of three or more types of power supply device are manufactured.
Further, the above-mentioned power supply devices are equipped with a cooling fan serving to release warm air within the device to the outside so as to avoid a drop in efficiency caused by heat. This cooling fan has a lifespan and must therefore be changed. Therefore, conventionally, a power supply device constituted such that the power supply connector of the cooling fan is removed to stop the drive of the cooling fan at the same time the cooling fan is removed has been proposed.
In cases where three or more other types of power supply device are manufactured as described above, not only is there an increase in the manufacturing costs, the post-production warehousing costs rise as the number of device types increases.
Furthermore, uninterruptible redundant power supply devices such as the one shown in FIG. 6, for example, are known from the prior art. This device comprises a primary side drive circuit A, which is constituted by a rectifier circuit 4 connected to a commercial AC power supply 1, an active filter circuit 5, and a switching element 8 and gate circuit 7 for supplying a voltage to a secondary side drive circuit B via a high frequency transformer 2; a secondary cell 3, which is constituted by a battery and so forth connected to the secondary side drive circuit B; and three DC-DC converters 50 that are connected in parallel with the single secondary side drive circuit B in order to permit a voltage step down by reducing the DC voltages of three different magnitudes for the load 14. 11 in the drawings is a rectifier diode, 12 is a smoothing choke coil, and 13 is a smoothing capacitor.
According to the above constitution, based on a relationship in which the secondary cell 3 and the three DC-DC converters 50 and so forth are connected to the single secondary side drive circuit B, not only is the secondary side drive circuit B then large and complex, when the DC-DC converters 50 fail, there is also the disadvantage that a DC voltage at a given point that is output via the DC-DC converters 50 cannot be extracted even during normal (ordinary) operation.
Furthermore, because the DC-DC converters 50 are interposed, there is the disadvantage that a total efficiency of approximately 55 to 64%, which is yielded by multiplying the efficiency of 75 to 80% of the secondary side DC-DC converters 50 by the efficiency of 75 to 80% of the primary side switching power supply circuit, is produced, and hence energy loss is a problem.
Further, when the cooling fan provided in the power supply device is changed, because the constitution is one in which the drive of the cooling fan is stopped by completely removing the cooling fan, injuries result when the cooling fan is being removed and a finger mistakenly strikes the rotating fan blades of the cooling fan during operation thereof. Further, although it may be assumed that care is taken in removing the cooling fan in order to avoid injury, because a large amount of time and effort is required in the operation to change the cooling fan, there is a margin for improvement.